In Japanese Patent Laid-open Publication No. 364171/1992 (EP-A-459136), it is disclosed that benzimidazole derivatives including 1-(cyclohexyloxycarbonyloxy)ethyl 2-ethoxy-1-[[2'-(1H-tetrazol-5-yl)biphenyl-4-yl]methyl]benzimidazole-7-car boxylate, which have AII (angiotensin II) antagonizing activity and anti-hypertensive activity and which are of value as a therapeutic drug for circulatory diseases such as hypertension, heart diseases (e.g. heart hypertrophy, heart failure, myocardial infarction, etc.), cerebral stroke, nephritis, etc., and it is described that a compound represented by the formula (IV), which is important as a synthetic intermediate of the benzimidazole derivatives, is produced by the reaction of an aminobenzoate derivative represented by the formula (III) shown below with a mono-halogenoalkylbiphenyl compound (4-bromomethylbiphenyl (BMB), etc.) represented by the formula (II) shown below. Also, in Japanese Patent Laid-open Publication No. 192170/1994 (EP-A-553879), it is described that 4-bromomethylbiphenyl (BMB) is produced by brominating 4-methylbiphenyl (MPB) in the presence of an azobis compound.
According to a known production method of a compound or a salt thereof represented by the formula (II), it was believed that it was advantageous to isolate and purify a final product which was used as a material of a drug, since a perhalogenated compound represented by the formula (II') shown below was produced in the yield of about 10-20% at the time of halogenation of a compound or a salt thereof represented by the formula (I) shown below. Therefore, it was essential to increase purity (usually more than 99%) of a compound or a salt thereof represented by the formula (II) by crystallizing said compound after the halogenating reaction. In addition, in order to recover loss while crystallizing the first crystals and to raise purification effect, it was necessary to isolate the second crystals from mother liquor and dry after isolating and drying the first crystals. So far, the thus purified compound or a salt thereof represented by the formula (II) has been used as a material in the next steps. However, according to the above method, it was necessary to isolate the crystallized compound or a salt thereof represented by the formula (II) by a centrifuge, etc. and thereafter to dry by a drier, etc.
On the other hand, a compound or a salt thereof represented by the formula (II) is useful as an intermediate compound for producing a drug such as anti-hypertensive agent. However, since a compound of the formula (II) wherein R.sup.1 is a cyano group, X is a direct bond and Y is a bromine atom is recognized to be strongly mutagenic and cause chromosomal aberrations, it was necessary to prevent the compound of the formula (II) from being exposed to workers producing the compound of the formula (II) and the environment.
According to a known method for producing a compound or a salt thereof represented by the formula (II), in order to prevent an isolated and purified compound or a salt thereof represented by the formula (II) from being exposed to the environment, a plant for producing said compound must be kept in isolation and, in order to prevent an isolated and purified compound or a salt thereof represented by the formula (II) from being exposed to the workers producing said compound, it was necessary to install an airtight centrifuge and drier, etc. However, it is very disadvantageous in view of industrial production to install such a special apparatus, etc. Moreover, according to a known method for producing a compound or a salt thereof represented by the formula (II), yield from a compound or a salt thereof represented by the formula (I) to a compound or a salt thereof represented by the formula (IV) is low and therefore not satisfactory as an industrial production method.